http://www.ck12.org Chapter 14. The Behavior of Gases
FIGURE 14.7
Robert Boyle is widely considered to be one of the founders of the modern
experimental science of chemistry. Among his many contributions is
observing the relationship between gas pressure and volume, described
by the gas law that bears his name.P×V = kThe k is a constant for a given sample of gas and depends only on the amount of the gas and the temperature. The
table below (Table14.1) shows pressure and volume data for a set amount of gas at a constant temperature. The
third column represents the value of the constant (k) for this data, which is always equal to the pressure multiplied
by the volume. As one of the variables changes, the other changes in such a way that the product of P×V always
remains the same. In this particular case, that constant is 500 atm•mL.
TABLE14.1: Pressure-Volume Data
Pressure (atm) Volume (mL) P×V = k (atm•mL)
0.5 1000 500
0.625 800 500
1.0 500 500
2.0 250 500
5.0 100 500
8.0 62.5 500
10.0 50 500A graph of the data in the table above (Table14.1) further illustrates the inverse relationship described by Boyle’s
Law (Figure14.8). Volume is plotted on the x-axis, and the corresponding pressure is indicated on the y-axis.
FIGURE 14.8
The pressure of a gas decreases as the
volume increases, making Boyle’s Law an
inverse relationship.Boyle’s Law can be used to compare changing conditions for a gas. We use P 1 and V 1 to stand for the initial pressure
and initial volume of a gas. After a change has been made, P 2 and V 2 stand for the final pressure and volume. The
mathematical relationship of Boyle’s Law becomes:
P 1 ×V 1 = P 2 ×V 2This equation can be used to calculate any one of the four quantities if the other three are known.
Sample Problem 14.1: Boyle’s Law